Temperature Aluminum Alloys Research Articles

An additively manufactured heat-resistant Al-Ce-Sc-Zr alloy: Microstructure, mechanical properties and thermal stability

In this study, a high-strength and heat-resistant Al–Ce–Sc–Zr alloy was designed and fabricated by additive manufacturing. The as-built alloy shows an excellent combination of strength and ductility compared to other Al–Ce-based alloys, including an ultimate tensile strength of 445 MPa, a yield strength of 344 MPa and an elongation of 10%. Even at 300 °C, the alloy still retains a superb tensile yield strength of 233 MPa, which is the best among the high-temperature aluminum alloys reported so far. The excellent performance is mainly attributed to a significant amount of fine, homogeneous and coarsening-resistant Al11Ce3 intermetallic nanoparticles formed during the rapid solidification process of laser additive manufacturing. The formation of coherent Al3(Sc, Zr) nano-precipitates and interfacial segregation at the interface of intermetallic nanoparticles during high temperature exposure further improve the high temperature properties of the alloy. Our work has the potential to provide design concepts for the development of novel high temperature aluminum alloys.

Elevated temperature aluminum alloys produced by water atomization

A new rapid solidification technology based on the use of modified water atomization followed by powder consolidation route has been developed recently and applied for manufacturing of a set of alloys for various applications. The paper analyses mechanical behavior in the range of 20–300 °C and microstructure of some elevated temperature Al–Fe–Ce base alloys produced by the above mentioned process in comparison with properties of similar alloys by other technologies. Mechanical properties were studied by tensile tests and Vickers hardness measurements. Microstructure and microchemistry of powders and powder metallurgy alloys were studied by electron microscopy, electron probe microanalysis and X-ray diffraction methods.

Evaluation of Strip Rolling Directly from the Semi-Solid State

The aim of this work is to study the solidification conditions necessary to produce good quality/low defect metal alloy strip when thixorolling directly from the semi-solid state. To facilitate the study lead/tin alloys were chosen for their relatively low operating temperature. The objective is to extrapolate these findings to the higher temperature aluminium alloys. Three alloys (70%Pb- 30%Sn, 60%Pb-40%Sn, 50%Pb-50%wtSn) were used particularly to study the influence of the solidification interval. The equipment consists of a two roll mill arranged as an upper and lower roller, where both rollers are driven at a controlled speed. The lower roller is fed with semi solid alloy through a ceramic nozzle attached to the lower end of a cooling slope. Several types of nozzle and their position at the roller were tested. This produced different solidifications and consequently different finished strip. The alloys were first cast and then poured onto the cooling slope through a tundish in order to create a continuous laminar flow of slurry and uniformity of metal strip quality. The pouring was tested at different positions along the slope. The cooling slope was coated with colloidal graphite to promote a smooth slurry flow and avoid the problem of adherence and premature solidification. The metallic slurry not only cools along the slope but is also initially super-cooled to a mush by the lower roller whilst at room temperatures, thus enabling thixorolling. It was also found that the nozzle position could be adjusted to enable the upper roller to also contribute to the solidification of the metallic slurry. However the rollers and the cooling slope naturally heat up. Temperature distribution in these zones was analysed by means of three thermocouples positioned along the cooling slope and a fourth in the base of the semi solid pool within the nozzle. The objective being to design an optimum pouring and cooling system. The formed strip was cooled down to room temperature with a shower of water. Microstructures of the thixorolling process were analysed. The differences in solidification conditions resulted in differing qualities of finished strip and corresponding defect types, all of which are a serious quality issue for the rolled product.

Some studies on Al–8.3Fe–0.8V–0.9Si alloy for near net shape casting

With the development of new generation high temperature aluminium alloys, simple techniques to produce them to near net shape by casting route have become necessary. It is well known that near net shape casting not only contributes to material saving but also to reduction of processing steps. Amongst the high temperature aluminium alloys, the Al–Fe–V–Si alloys system has attracted considerable interest due to its potential in automotive and aerospace applications. These alloys are generally prepared through the complex rapid solidification–powder metallurgical processing route. Thus, although the alloys possess good elevated temperature strength, ductility, fatigue and fracture toughness they have not found industrial application. An alternative method of conventional solidification for producing these alloys has been attempted in this work. A novel structural modification technique has been tried out with Mg/Ni–Mg master alloy to bring about alteration and refinement of the precipitate particles, which are otherwise ten-armed star-shaped and adversely affect the mechanical properties, to favourable cuboidal, hexagonal or other compact forms. It was observed that a number of arrest points occur in the cooling curve of the alloy, indicating that a variety of phases such as Al 12(Fe,V,Si) 6(Si,Mg) 5, Al 15(Ni,V,Fe) 6(Si,Mg), Al 3(Fe,V,Ni,Si,Mg) form during cooling. Quenching experiments were performed to identify the details of the phases formed. The features of the phases were studied using scanning electron microscope/EDAX and X-ray diffraction. Important properties required for near net shape casting such as the thermal expansion coefficient, fluidity, etc., have been studied and correlated with the phases.

Valence electron structure analysis of the cubic silicide intermetallics in rapidly solidified Al-Fe-V-Si alloy

The application of rapid solidification for the development of elevated temperature aluminum alloys has resulted in the emergence of several alloys based on the Al-Fe alloy system. Of particular interest are Al-Fe-V-Si alloys which have excellent room temperature and high temperature mechanical properties. In a pioneering study, Skinner et al. showed the stabilization of the cubic phase in ternary Al-Fe-Si alloy by the addition of a quaternary element, vanadium. The evolution of the microstructure in these alloys both during rapid solidification and subsequent processing is of crucial importance. Kim has demonstrated that the composition of the silicide phase in rapidly solidified Al-Fe-V-Si alloy is very close to Al{sub 12}(Fe,V){sub 3}Si with the body centered cubic (bcc) structure. The structure is closely related to that of quasicrystals.In view of the structural features and the relationship between the {alpha}{sub 12} and {alpha}{sub 13} phases, the researching emphasis should firstly be put on the {alpha}{sub 12} phase. In this paper the authors analyzed the {alpha} {minus}(AlFeSi)({alpha}{sub 12}-type) phase from the angle of atomic valence electron structure other than the traditional methods of obtaining the diffraction spots of the phase. Several pieces of information were obtained about the hybrid levels and bond natures ofmore » every kind of atom in the {alpha} {minus}(AlFeSi) phase. Finally the authors explained the phenomenon which V atom can substitute for Fe atom in the {alpha}{sub 12} phase and improve the thermal stability of the phase in Al-Fe-V-Si alloy.« less

Extrusion processing parameter–mechanical property correlations in rapidly solidified Al–6·7Fe–5·9Ce and Al–6·2Fe–5·9Ce–1·63Si (wt-%) alloy powders

High temperature aluminium alloys containing iron and cerium additions have promising mechanical properties, particularly with regard to thermal stability. Development of these alloys has been possible because of advances in rapid solidification technology. The advantage of rapid solidification is that it produces extended solid solubility or a high volume fraction of strengthening dispersoids depending on the cooling rate. To retain the microstructural advantages of rapid solidification, it has generally been thought necessary to process these alloys at the lowest possible temperature. The present work indicates that for optimum strength levels this is correct but that the greater homogeneity of microstructure produced by higher processing temperature leads to improved ductility and toughness. The present investigation was undertaken to find suitable extrusion processing conditions for two rapidly solidified high temperature aluminium alloys having the compositions Al–6·7Fe–5·9Ce and Al–6·2Fe–5·9Ce–1·63Si (all wt-%). Silicon was added to Al–Fe–Ce in an attempt to form the Al12(Fe,Ce)3Si phase, which if formed might improve the thermal stability of the alloy (similar to the Al12(Fe,V)3Si phase in the Al–Fe–V–Si system). Both the alloys were extruded in the temperature range 400–500°C at a constant extrusion ratio of approximately 10:1 and ram speed of 3 mm s−1. The room temperature mechanical properties of all the extrudates were measured for both alloys and the values obtained were compared with those for other high temperature aluminium alloys such as Al–5Cr–2·2Zr and Al–8·3Fe–4·8Zr. High temperature tensile properties were measured for extrudates processed at 400 and 450°C. The results obtained for the low temperature (400°C) extrudate were found to be satisfactory when compared with US Air Force Materials Laboratory (AFML) goals for high temperature aluminium alloys. Attempts have been made to explain the properties on the basis of the microstructures of the extrudates, which were characterised using transmission and scanning electron microscopy and X-ray diffraction.MST/1615

High temperature aluminium alloys for aerospace applications : P.S. Gilman, (Allied-Signal Intl, Morristown, New Jersey, USA)

High temperature aluminium alloys for aerospace applications : P.S. Gilman, (Allied-Signal Intl, Morristown, New Jersey, USA)

Fabrication of rapidly solidified high temperature aluminium alloys

Fabrication of rapidly solidified high temperature aluminium alloys

Applications of Rapidly Solidified High Temperature Aluminum Alloys

Applications of Rapidly Solidified High Temperature Aluminum Alloys

Elevated temperature aluminum alloys for advanced fighter aircraft

Elevated temperature aluminum alloys are being developed for aircraft structural applications in the 300 F to 600 F temperature range. Material properties of various alloy systems and product forms display excellent room and elevated temperature strength, fracture toughness, and corrosion resistance. These materials are considered for applications in the aft fuselage of an Advanced Tactical Fighter (ATF). Design trade studies were conducted for a center keel beam structure between the engine compartments. Results show potential weight and cost savings of 12.8 percent and 46.5 percent, respectively, for a structure fabricated from elevated temperature aluminum alloys as opposed to titanium alloys. Additional weight and cost savings can be achieved by using hot molded metal matrix composite (MMC) Al/SiCf beam caps.

Effect of strain rate on tensile ductility for a series of dispersion-strengthened aluminum-based alloys

Rapid solidification processing, in the manufacture of elevated temperature aluminum alloys, results in significant supersaturation of solute elements in the aluminum matrix solid solution. These levels are shown to alter significantly the deformation characteristics of this class of alloys through the phenomenon of dynamic strain aging (DSA). That is DSA reduces tensile ductility at intermediate temperatures. The temperature ranges are found to be dependent on the solute element in solid solution and the strain rate of testing.

High performance aerospace alloys via rapid solidification processing

Recent progress in the rapid solidification processing of metallic materials has opened new horizons for alloy design, expanding the ranges of possible microstructures and alloy compositions beyond those readily achieved through conventional technology. Alloy systems incorporating high volume fractions of ultrafine dispersed phases can now be produced, yielding corrosion and oxidation resistances and combinations of toughness and elevated temperature strength hitherto considered impossible. The particular examples discussed here are those of high strength corrosion-resistant magnesium alloys, AlLi alloys of reduced density, high temperature aluminum alloys and titanium alloys. In reviewing the design of these alloys, we shall discuss the interplay between the selection of alloy chemistry, the solidification kinetics characteristic of various rapid solidification powder production processes and the thermomechanical processing of the rapidly solidified powders. These three areas form links in a continuous chain, none of which can be neglected if the final product is to have the desired properties.

High-temperature properties of rapidly solidified Al-Be alloys

Rapidly solidified Al-Be binary alloys (10%, 20%, and 40%, Be by weight) have been produced by melt-spinning techniques. The microstructures have been evaluated and the elevated temperature mechanical properties have been characterized over a range of strain rates. Despite the fact that the materials exhibited duplex microstructures resulting from high-temperature processing, they showed behaviour typical of dispersion strengthened alloys. The mechanical properties at elevated temperature can accurately b8 described by the equation\(\dot \varepsilon = A(\sigma /E)^{12} \) exp (−120 kJ mol−1/RT), where\(\dot \varepsilon \) is the deformation rate,σ is the stress,E is the modulus,A is 8 material constant, andRT has its usual meaning. A direct comparison of the deformation properties was made between binary Al-Be composition and pure aluminium as baseline, as well as between Al-Be and some high temperature aluminium alloys. The Al-Be alloys do not exhibit good high-temperature strength when compared with other high-temperature aluminium alloys, e.g. Al-Fe-Co alloys. This is a result of particle coarsening and agglomeration during processing and testing.

High-Performance Light-Weight Allovs by Rapid Solidification Processing

AbstractThere exists a great need for the development of high-performance light-weight alloys for aerospace application. Application of rapid solidification processing (RSP) has shown a strong potential for the improvement of properties of existing alloys and also for the development of novel alloy systems with superior properties. The present paper reviews the Allied-Signal's activities in the development of high-performance lightweight alloys by RSP. Examples include (i) high temperature aluminum alloys, (ii) aluminum-lithium alloys and (iii) corrosion resistant magnesium alloys.

Effect of Rolling Parameters on the Properties of Al-Fe-V Sheet Rolled on an Experimental Mill

ABSTRACTIn recent years, interest in high temperature aluminum alloys has increased. However, nearly all the data available is for simple extrusions. This paper looks at the properties of sheet made from a rapidly solidified Al-10Fe-2.5V-2Si alloy. The sheet is made by direct forging followed by hot rolling, this is readily scalable, so allowing the production of large sheet. The room temperature strength and fracture toughness of the sheet are comparable to those of 2014-T6. The high temperature strength, specific stiffness and corrosion resistance are excellent. Recently, improved thermomechanical processing and new alloys have allowed higher strengths and fracture toughness values to be obtained.